A year in the life of the low-mass X-ray transient Aql X-1

Abstract

The Swift satellite monitored the quiescence of the low-mass X-ray binary transient Aql X-1 on a weekly basis during the March-November 2012 interval. A total of 42 observations were carried out in the soft X-ray (0.3-10 keV) band with the X-ray Telescope on board Swift. We investigated the X-ray variability properties of Aql X-1 during quiescence by tracking luminosity variations and characterising them with a detailed spectral analysis. The source is highly variable in this phase and two bright flares were detected, with peak luminosities of ~4x10^{34} erg s^{-1} (0.3-10 keV). Quiescent X-ray spectra require both a soft thermal component below ~2 keV and a hard component (a power law tail) above ~2 keV. Changes in the power law normalisation alone can account for the overall observed variability. Therefore, based on our data set, the quiescent X-ray emission of Aql X-1 is consistent with the cooling of the neutron star core and with mechanisms involving the accretion of matter onto the neutron star surface or magnetosphere.

8 pages, 7 figures, 4 tables; accepted for publication on MNRAS

References in corpus (3)

• Discovery of coherent millisecond X-ray pulsations in Aql X-1
• The behavior of subluminous X-ray transients near the Galactic center as observed using the X-ray telescope aboard Swift
• The Variable Quiescent X-ray Emission of the Neutron Star Transient XTE J1701-462

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